Human and bovine milk can replace serum as a supplement for the growth of cells in culture. Milk is more efffective in supporting the growth of epithelial cells than fibroblasts. Human milk and bovine colostrum contain growth factors that stimulate DNA synthesis and cell division in cultured cells. The growth factors appear to be polypeptides and can be isolated and characterized. Human milk contains at least 3 growth factors, one of which is structurally similar to epidermal growth factor (EGF). Bovine colostrum has at least one growth factors and it appears to be structurally different than EGF. The specific aims of the proposed research are: 1) continuation of experiments involving the purification of human and bovine milk growth factors; 2) purification of growth factors that stimulate the growth of epithelial cells; 3) biochemical and biological characterization of milk-derived growth factors and determination if one of these factors is identical to EGF-uragastrone; 4) production of antibodies to milk-derived growth factors; 5) continuation of experiments involving the growth of cells in serum-free milk-supplemented medium, with emphasis on epithelial cells; 6) the study of the biosynthesis of milk-derived growth factors by mammary epithelial cells; 7) the development of techniques for the quantitative sustained release of growth factors from small biocompatible polymers for use in vivo. The long-range goal of these studies is to determine the physiological role of milk-derived growth factors and to use the purified growth factors for the stimulation of the growth of specific cell types of vivo. Hopefully, the biochemical analysis of the structure and function of biologically active growth-promoting polypeptices will help to elucidate the physiological role of milk in the growth and development of the newborn.